Use test::RunLoop in pc/rtp_transceiver_unittest.cc and fix shadowing

Bug: webrtc:469327588
Change-Id: Iecfafc8824af9a91e420c7f5b5604cc96a6a6964
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/464461
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Auto-Submit: Evan Shrubsole <eshr@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#47477}

pc/rtp_transceiver_unittest.cc

diff --git a/pc/rtp_transceiver_unittest.cc b/pc/rtp_transceiver_unittest.cc
index 855bc2f..a7abb5b 100644
--- a/pc/rtp_transceiver_unittest.cc
+++ b/pc/rtp_transceiver_unittest.cc
@@ -61,6 +61,7 @@
 #include "test/create_test_environment.h"
 #include "test/gmock.h"
 #include "test/gtest.h"
+#include "test/run_loop.h"
 
 using ::testing::_;
 using ::testing::ElementsAre;
@@ -99,9 +100,10 @@
     return &codec_lookup_helper_;
   }
 
- private:
-  AutoThread main_thread_;
+ protected:
+  test::RunLoop main_thread_;
 
+ private:
   static PeerConnectionFactoryDependencies MakeDependencies() {
     PeerConnectionFactoryDependencies d;
     d.network_thread = Thread::Current();
@@ -129,7 +131,6 @@
   EXPECT_CALL(*channel1, mid()).WillRepeatedly(ReturnRef(content_name));
   EXPECT_CALL(*channel1, SetRtpTransport(_)).WillRepeatedly(Return(true));
 
-
   transceiver->SetChannelForTest(std::move(channel1),
                                  [&](const std::string& mid) {
                                    EXPECT_EQ(mid, content_name);
@@ -253,9 +254,6 @@
         media_engine()->voice().GetRtpHeaderExtensions(&env().field_trials()),
         /* on_negotiation_needed= */ [] {});
   }
-
- protected:
-  AutoThread main_thread_;
 };
 
 // Basic tests for Stop()